The present invention relates generally to the fields of medicine and virology. More particularly, it concerns methods and combination compositions for the treatment of viral infections, especially retroviral infections, for treatment of individuals who are treatment experienced and resistant to current protocols, and for post-exposure prophylaxis.
Antiviral agents are generally modeled to inhibit viral replication within an infected cell. Effective antiviral agents specifically target steps within the viral replication pathway thereby inhibiting or hindering viral replication within infected host cells while having a minimal cytotoxic effect on the host. Thus, many antiviral agents are specific inhibitors to virus-specific enzymes or proteins, such as viral DNA or RNA polymerases, or cleavage enzymes for viral capsid protein. Nucleoside analogues, for example, have been developed that target particular enzymes in the viral replication pathway by mimicking a natural substrate of the enzyme.
Adverse toxicity effects exist with the administration of most antiviral agents, particularly at the dosage levels required to attain effective antiviral chemotherapy, due to a lack of viral specificity. Presently, there are very few antiviral agents that are considered to be efficacious, i.e. agents having a high level of viral toxicity and a low level of cytotoxicity. Such agents include iododeoxyuridine, adenine arabinoside and trifluorothymidine, all used to treat herpetic keratitis, acyclovir which is used in the treatment of genital herpes and mucosal and cutaneous herpes infections in the immunocompromised patient, and amantadine which is used to treat influenza A. These antiviral agents have a relatively low level of cytotoxicity in comparison to other antiviral agents. Adverse toxicity effects associated with acyclovir, for example, include transient impairment of renal function, nausea and vomiting, reversible neurological reactions, raised liver enzymes, rashes and increased hematological indexes.
Human immunodeficiency virus (HIV) is a prototype for pathogenic retroviruses, i.e., viruses that use reverse transcription to replicate. Reverse transcription mechanisms are required by those viruses having an RNA genome wherein the RNA is copied by a polymerase into DNA for subsequent replication. Certain DNA viruses use, in part, reverse transcription mechanisms to replicate such as, for example, hepatitus B virus. Reverse transcriptase is the virally-encoded polymerase used by retroviruses for this purpose.
Two nucleoside analogue reverse transcriptase inhibitors in combination with a potent protease inhibitor are generally recommended to achieve suppression of viral replication in current treatment protocols for HIV-1 infected individuals. Nucleoside analogue reverse transcriptase inhibitors in current use are described infra (adapted from Scientific American Medicine, January 1999, Chapter 11 www.samed.com, Scientific American Inc.).
Azidothymidine (AZT, zidovudine) is administered at a dosage of 600 mg orally daily in two divided doses. The major dose-limiting toxicity of AZT is on bone marrow. Clinical trials demonstrate that therapy delays clinical evidence of disease progression in previously untreated persons with CD4+T cell counts below 500 cells/mm3. AZT is generally not used as a single agent.
Dideoxyinosine (ddI, didanosine) is administered orally as an inosine prodrug and is formulated with a buffer directed at gastric acid because of the acid lability of dideoxyadenosine. The major toxicities associated with ddI are pancreatitis and peripheral neuropathy. DdI was demonstrated to be superior to AZT in antiviral and immunomodulatory effects and to provide additional clinical benefits to patients who have used AZT.
Dideoxycytosine (ddC) is a nucleoside analogue reverse transcriptase inhibitor that exhibits potent antiretroviral activity in vitro. Dose escalation of ddC is limited by peripheral neuropathy, however, and ddC is therefore used only in combination regimens or for the treatment of patients who are intolerant of, or unresponsive to, other antiretrovirals. DdC is administered at a dosage of 0.75 mg three times daily and has been used extensively in combination regimens for persons with advanced AIDS who are intolerant of other antiretroviral chemotherapeutic agents.
D4T (stavudine), a thymidine analogue, has been investigated in patients with moderate to advanced HIV-1 infection, especially those with previous AZT experience. However, peripheral neuropathy is a major side effect.
Lamivudine (3TC) is well tolerated and results in acute reductions in plasma HIV-1 RNA levels. However, a single mutation in reverse transcriptase at position 184 results in a 100-fold to 1,000-fold decrease in susceptibility to lamivudine. Any measurable degree of viral replication in the presence of the drug results in the rapid emergence of resistant mutations. Lamivudine is associated with suppression of the erythroid and myeloid elements of bone marrow.
Abacavir is usually given as 600 mg, orally, daily in 2 divided doses. The drug is compromised by mutations in the reserve transcriptase (RT) gene. The efficacy of abacavir is compromised by the emergence of reverse transcriptase drug-resistant viral variants. In vitro studies have shown that the single mutations 65R, 74V, 184V, and 115F in the RT gene confer 2-3xe2x80x94fold decreases in susceptibility to abacavir. Mutants harboring 2 or 3 of these mutations exhibit approximately 10-fold resistance to the drug. In clinical studies, patients with more than 2 RT mutations showed a markedly inferior response to abacavir containing regimens.
F-ddA (lodenosine) is a fluoridated compound with similar structure and activity to ddI. F-ddA is not FDA-approved at the present time. Unlike ddI, stomach acids do not degrade F-ddA, so it can be administered without an antacid, thereby avoiding side effects attributable to the use of a buffer. Resistance to F-ddA is slow to emerge and the drug has shown in vitro activity against strains of HIV resistant to AZT, ddI, and ddC.
In light of rapid rates of viral replication, the highly error-prone HIV-1 reverse transcriptase, and the inability of currently available antiretroviral agents to completely inhibit HIV-1 replication, the development of resistance to antiretroviral drugs has been an inevitable consequence of drug exposure. Viral variants resistant to all antiretroviral agents in active use have been demonstrated (see the Scientific American Medicine, Chapter 11 cited herein, for a discussion of molecular mechanisms by which the virus may develop resistance to antiretroviral drugs).
The above-described protocols focus primarily on the interruption of the virus life cycle, through the inhibition of viral enzymes involved in viral replication. Though this has resulted in some control of the virus, over one-fourth of treatment naive individuals are infected with a virus with reduced susceptibility to one or more of the currently FDA-approved drugs. Moreover, up to 3% of newly diagnosed individuals are infected with a virus that is resistant to drugs in all types of currently approved therapies. Unfortunately, many of the current drugs in development are similar to currently existing therapies, and are likely to offer little to the current armamentarium of treatment.
Another approach to control HIV-1 replication is the targeting of cellular enzymes, a strategy based on the fact that the virus is dependent on the host cellular machinery for replication. Since host enzymes do not mutate at the same rate that viral proteins do, a cellular approach may result in controlling the emergence of drug-resistant viruses. Clinical trials using hydroxyurea and ddI have been reported in the treatment of HIV-1 infection (Lori, et al., JAMA, 277:1437-38, 1997; Vila, et al., Lancet, 348(9021:203-4, 1996). U.S. Pat. No. 5,736,527 relates to a method of treating HIV in humans by administration of ddI and hydroxycarbamide (hydroxyurea, (HU)), however, a mixture of hydroxycarbamide with AZT was found not to modify a viral replication profile compared to AZT alone. Clinical application of the combination of ddI and HU has been limited because of the antiproliferative and anti-DNA synthesis activity associated with HU. In addition, immunological reconsititution in patients that are responsive to the viral treatment is blunted. In patients with severe T-cell depletion, treatment with HU has resulted in increased bone marrow toxicity and CD4+T-cell depletion such that this combination is rarely used in patients with HIV-induced immunodeficiency. Toxicities possibly associated with HU, such as pancreatitis and increased liver function tests, highlight the need for new therapies in pursuing adjunctive antiretroviral therapy involving cellular enzyme inhibition or cell cycle modification.
A major target of HIV-1 is the CD4+T lymphocytes and monocyte-derived macrophages. It is thought that the majority of circulating lymphocytes are non-dividing, quiescent (resting) cells. Viral entry and transcription occur as efficiently in resting lymphocytes as in activated lymphocytes, but integration of the proviral DNA in the host genome only takes place in activated cells. Therefore, resting cells represent a major reservoir for HIV-1 infection and, upon cellular activation, constitute a source of new virus progeny. A large proportion of the HIV-1 genome in infected individuals exists as full length, extrachromosomal DNA, which retains the ability to integrate upon activation of the host cell. In addition, infected macrophages represent a long-term source of virus, since these cells do not die upon HIV-1 infection. Therefore, effective treatment protocols necessarily must address the presence of the virus in resting and long-term cellular reservoirs.
Retroviral, especially HIV, therapy is now thought to be a life-long process. Therefore, it is crucial to develop effective treatments that can be successfully administered for long periods of time for the suppression of retroviruses, and in particular, the prevention and/or inhibition of HIV. Further, it would be desirable to eliminate, or at least minimize, the cytotoxicity associated with the administration of antiviral agents otherwise determined to be effective. It is generally recognized that the toxicity of an antiviral agent may be avoided or at least minimized by administration of a reduced dose of the antiviral agent; however, it is also recognized that the effectiveness of an antiviral agent generally decreases as the dose is reduced.
Herpes simplex virus (HSV) types 1 and 2 are persistent viruses that commonly infect humans. HSV type 1 causes oral xe2x80x9cfever blistersxe2x80x9d (recurrent herpes labialis), and HSV type 2 causes genital herpes, which has become a major venereal disease in many parts of the world. Although it is uncommon, HSV can also cause encephalitis, a life-threatening infection of the brain. A most serious HSV-caused disorder is dendritic keratitis, an eye infection that produces a branched lesion of the cornea, which can in turn lead to permanent scarring and loss of vision. Ocular infections with HSV are a major cause of blindness.
Hepatitis is a disease of the human liver. It is manifested with inflammation of the liver and is usually caused by viral infections and sometimes by toxic agents. Hepatitis may progress to liver cirrhosis, liver cancer, and eventually death. Several viruses such as hepatitis A, B, C, D, E and G are known to cause various types of viral hepatitis. Among them, HBV and HCV are the most serious. HBV is a DNA virus and HCV is a RNA virus.
Hepatitis C is difficult to treat, and it is estimated that there are 500 million people infected with it worldwide. No effective immunization is currently available, and hepatitis C can only be controlled by preventive measures such as improvement in hygiene and sanitary conditions, and interruption of the route of transmission. At present, the only acceptable treatment for chronic hepatitis C is interferon which requires at least six months of treatment and/or ribavarin which can inhibit viral replication in infected cells and also improve liver function in some people. Treatment with interferon with or without ribavarin, however, has limited long term efficacy and has a low response rate.
Hepatitis B virus infection leads to a wide spectrum of liver injury. Moreover, chronic hepatitis B infection has been linked to the subsequent development of hepatocellular carcinoma, a major cause of death. Current prevention of HBV infection is a hepatitis B vaccination which is therapeutically effective. However, vaccination is not effective in treating those already infected (i.e., carriers and patients). Many drugs have been used in treating chronic hepatitis B and none have been proven to be effective, except interferon.
Treatment of HCV and HBV with interferon has limited success and has frequently been associated with adverse side effects such as fatigue, fever, chills, headache, myalgias, arthralgias, mild alopecia, psychiatric effects and associated disorders, autoimmune phenomena and associated disorders and thyroid dysfunction. Because the interferon therapy has limited efficacy and frequent adverse effects, a more effective regimen for the treatment of these viral infections is needed.
Because of the above problems in the art, current protocols are not completely satisfactory, and the present inventors provide improvements herein.
AZT: zidovudine, 3xe2x80x2-azido-2xe2x80x2,3xe2x80x2-dideoxythymidine, azidothymidine
ddA: 2xe2x80x2,3xe2x80x2-dideoxyadenosine
ddC: 2xe2x80x2,3xe2x80x2-dideoxycytosine
ddG: 2xe2x80x2,3xe2x80x2-dideoxyguanosine
ddI: 2xe2x80x2,3xe2x80x2-dideoxyinosine, didanosine
ddT: 2xe2x80x2,3xe2x80x2-dideoxythymidine (DT4)
ELISA: Enzyme-linked immunoadsorbent assay
HIV: Human immunodeficiency virus
HU: Hydroxyurea
MDM: Monocyte-derived macrophage
PBMC: Peripheral blood mononuclear cell
PHA: Phytohemagglutinin
RNA: Ribonucleic acid
RV: Resveratrol
The present invention relates to a combination of an agent that promotes DNA synthesis in a virally-targeted cell in combination with a nucleoside analogue having antiviral activity, the administered combination for treating a viral infection in a subject in need thereof. Surprisingly, the present inventors have found that such a combination is minimally antiproliferative, yet has very potent antiviral activity. In particular, the invention relates to a method of treating, by preventing and/or inhibiting the spread of, retroviral infections, including HIV, by exposing a cell population, including cells infected by a retrovirus such as, for example, HIV, to such a combination. Further, the invention encompasses the treatment of HIV-infected and AIDS patients with such a combination in order to inhibit viral replication and HIV disease progression. A virally-targeted cell is a cell in which virus is present and is infective or potentially infective.
The present invention provides for the ability to suppress viral production for periods of time post-treatment, and to suppress nucleoside-resistant strains of virus in treatment-experienced subjects, with minimal toxicity. Furthermore, since one component of the combination compositions of the present invention targets cellular machinery of the host, rather than the virus, the present inventors expect that viral resistance to this drug combination essentially would not occur.
A method of treating a viral infection in a subject in need thereof, or for inhibition of a productive viral infection in a subject in need thereof by inhibition of viral production in a cellular reservoir of the subject is provided by the invention. The method comprises administering to the subject a combination of an agent that promotes DNA synthesis in a virally-targeted cell and a nucleoside analogue having antiviral activity. The method may further comprise the step of terminating the administering of the combination, thereby inducing a post-treatment period of viral incompetence.
A further aspect of the invention is a composition comprising a hydroxylated stilbene in an amount so as to provide an in vivo plasma concentration of 1 xcexcM-25 xcexcM and a nucleoside analogue having antiviral activity in an amount so as to provide an in vivo plasma concentration of 0.01 xcexcM-100 xcexcM.
Combination compositions of the present invention may comprise lower doses of the active antiviral nucleoside analogue while maintaining a level of antiviral activity that is characteristic of a higher dose. As a result, the cytotoxicity typically associated with the administration of an antiviral nucleoside analogue is minimized by the administration of combination compositions of the present invention. Combination compositions may comprise a usual dosage of antiviral nucleoside analogue in combination with a DNA synthesis-promoting agent to achieve a level of antiviral activity that is greater than that normally required while maintaining an acceptable level of cytotoxicity. An increased level of antiviral activity is useful particularly in the treatment of a viral infection caused by a strain that has developed a resistance to the administered nucleoside analogue.
The combination composition of the present invention demonstrates minimal antiproliferative activity, demonstrates enhancement of DNA synthesis activity at doses having antiviral activity, is useful for immunocompromised patients, and is useful for enhancing the in vivo capacity for immune reconstitution in a subject in need thereof.